The continued development, study, and analytical applications of novel anion/gas/polyion selective polymer membrane/film-based electrochemical and optical sensors are proposed. Research will build upon several exciting breakthroughs made during the most recent period of support that have included: 1) the ability to rapidly screen for the presence of high charge density of polyanion impurities (e.g., oversulfated chondroitin sulfate (OSCS)) within commercial biomedical grade heparin preparations using potentiometric polyanion sensor technology; 2) the use of rhodium (III) metalloporphyrin complexes as the most selective binding agents discovered to date for preparing potentiometric (and potentially optical) nitrite ion sensors; and 3) the adaptation of a new pulstrode type potentiometric measurement technology to enhance the analytical response properties of anion and polyion sensitive polymeric membrane electrodes. Efforts during the next phase of this long-term program will include both fundamental and applied studies and will concentrate on: 1) examining approaches to use the new polyanion sensor-based method to quantify the concentration of OSCS and potentially other high-charge density polyanion impurities in biomedical heparin preparations, and also assess whether a previously reported optical heparin sensing polymer film technology can be employed for similar measurements; 2) further optimize the utility of rhodium(III) metalloporphyrins as ionophores in polymeric films for developing highly selective electrochemical and optical sensors for nitrite (using capped tetraphenylporphyrins as ionophores), and demonstrating the use of such sensors as simple detectors in a novel gas/biosensing system to monitor very low levels of gas phase nitric oxide (NO), potentially in exhaled breath; and 3) assessing the use of a new pulstrode instrumental control method to enhance the potentiometric selectivity of various ionophore-based polymeric membrane anion sensors, and also to prepare fully reversible polyanion/polycation sensors that can be used to continuously monitor heparin in blood and for detecting protease activities. It is anticipated that results derived from the research in these areas will continue to provide an array of new and simple sensors that can be employed for important biomedical measurements in complex physiological and other types of samples.